Inner tubes have been used for decades in pneumatic tires. Inner liners have been used for many years in tubeless pneumatic vehicle tires to prevent the escape of air used to inflate the tire, thereby maintaining tire pressure. For example, see U.S. Pat. No. 3,960,628, the inner liner 25 in FIG. 1. Materials which are relatively impermeable to air are used in said inner liners and inner tubes and can include butyl rubber and halobutyl rubbers. U.S. Pat. No. 3,808,177 reveals polymers which are also relatively impermeable.
The inner liner is normally prepared by conventional calendering techniques and as a result often requires the use of a processing aid. Materials used in the preparation of inner tubes also normally require a processing aid.
With the introduction of metal-reinforced tires, for example, steel-belted radial tires, problems have arisen regarding metal-to-rubber adhesion and metal cord failure.
It is well known that moisture can cause the breakdown of the adhesion system between the metal of the reinforcement elements and the rubber adjacent thereto, which can result in the failure of the tire. It is also well known that moisture can cause corrosion of the metal to such a degree that total failure of the reinforcement element itself can occur.
Various methods have been used to prevent the breakdown of this adhesion system and to prevent corrosion of the metal such as by treatment of the metal itself.
There is a need, however, for other techniques to prevent the failure of metal-reinforced pneumatic tires.
Indeed, it has been found that low water vapor, or moisture, and low air diffusion or permeability are important as tire inner liner characteristics for metal, particularly steel cord in its brass coated state, reinforced rubber tire.
However, it is sometimes important to improve the processability of the liner rubber compound or compounded rubber, during its mixing, calendering and/or shaping step(s). Although such processability improvement for rubber compounds is conventionally achieved by adding or increasing rubber processing oil, such addition generally degrades moisture and/or air diffusion through the prepared inner liner in the metal cord reinforced rubber tire which, in turn, generally degrades the metal to rubber adhesion.
Therefore, it is an object of this invention to provide a metal reinforced pneumatic rubber tire having an enhanced inner liner.
It is a further object of the present invention to provide a method of preventing or retarding corrosion of the metal reinforcement element of metal-reinforced pneumatic vehicle tires and the failure of the adhesion system between the element and the rubber adjacent thereto. It is also an object of the present invention to provide a special inner liner or inner tube for steel-belted pneumatic vehicle tires. Other objects will become apparent as the description proceeds.